Browsing by Subject "Animal science"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
  • Thumbnail Image
    Item
    Effects of feeding moderate-energy high-forage diets with reduced DCAD for twenty-one or forty-two days prepartum on mineral homeostasis and postpartum performance
    (2012-08) Weich, William Douglas
    In spite of decades of research, feeding strategies that prevent milk fever and hypocalcemia in the transition cow are not completely understood. Extended negative dietary cation-anion difference (DCAD) feeding in the prepartum diet would allow producers to utilize a one group dry cow pen; reducing social stress on cows while providing protection against hypocalcemia. High-fiber prepartum diets including wheat straw are inherently low in potassium and have been shown to reduce risk of hypocalcemia. Few studies examine effects of inclusion of DCAD lowering feed additives in low-potassium dry cow diets. The combined effects of extended low DCAD in a low-potassium diet remaining unexplored. To test objectives, Holstein and Holstein-cross dairy cows (n = 49) blocked by breed, parity, body weight, body condition score and previous milk production were randomly assigned to one of three treatments 42 d prior to expected calving to evaluate effects of feeding negative DCAD for 21 or 42 d during the dry period on postpartum production and mineral homeostasis. Treatments included: 1) CON, DCAD = +12 mEq/100 g DM, 2) 21-ND, DCAD = +12/-16 mEq/100 g DM, 3) 42-ND, DCAD = -16 mEq/100 g DM. Prepartum diets were similar in nutrient composition, averaging 17.0% CP, 42.0% NDF and 1.5 Mcal/kg DM. Control and anionic diets were achieved using two isonitrogenous protein mixes: 1) 97.5% soybean meal and 2) 52.8% Bio-Chlor® (Church and Dwight, Franklin Lakes, NJ), 45.8% soybean meal. CON was fed high DCAD prepartum for 42 d. 21-ND received high DCAD for the first 21 d of the dry period, and the anionic diet from d 22 until calving. 42-ND received anionic diet for the entire dry period. Supplementing anions induced a metabolic acidosis reducing urine pH for 21-ND and 42-ND compared to CON. Prepartum DMI was not affected by prepartum anionic supplementation. Postpartum DMI tended to be higher for anionic diets than the control diet (20.1 vs. 18.1 kg/d). Prepartum anionic supplementation significantly affected milk production, with CON, 21-ND and 42-ND averaging 39.1, 45.7 and 43.8 kg/d, respectively. Also, overall postpartum total blood calcium increased with extended feeding of the anionic diet. Blood magnesium through calving was highest for 42-ND. Diets had no effect on postpartum energy-related metabolites or liver composition, however overall means for liver total lipid, liver triglyceride and blood ketone concentrations were highest for CON. These data suggest low DCAD in high fiber diets for 21 or 42 d during the dry period can have positive effects on postpartum mineral homeostasis and production.
  • Thumbnail Image
    Item
    Equine grazing prefences and forage quality of cool-season forage grasses.
    (2012-05) Allen, Elizabeth
    Abstract summary not available
  • Thumbnail Image
    Item
    Fate and biological activity of antibiotics used in ethanol production.
    (2012-06) Compart, Devan Marie Paulus
    Antibiotics are utilized in ethanol production to control unwanted bacteria from competing with yeast for nutrients during ethanol fermentation. However, there is no published scientific information on whether antibiotic residues in distillers grains (DG) co-products from ethanol production retain their biological activity. Therefore, the objective of this study was to quantify the concentration of various antibiotic residues in DG and determine if those residues are biologically active. Twenty distillers wet grains and 20 distillers dried grains samples were collected quarterly from nine states and 43 ethanol plants in the United States. Samples were analyzed for DM, CP, NDF, crude fat, S, P, pH, and titratable acidity. Samples were also analyzed for the presence of erythromycin, penicillin G, tetracycline, tylosin, and virginiamycin using liquid chromatography and mass spectrometry. Additionally, virginiamycin residues were determined using an FDA-approved method of analysis. Samples were further analyzed for biological activity by exposing sample extracts to varying levels of the sentinel bacteria Escherichia coli ATCC 8739 and Listeria monocytogenes ATCC 19115. Residues that inhibited bacterial growth were considered to have biological activity. Data were analyzed using the mixed procedure of SAS 9.2. Physiochemical characteristics varied among samples, but were consistent with previous findings. Ten percent of samples contained erythromycin residues at concentrations up to 0.87 ppm on a DM basis. Less than one percent of the samples contained penicillin G residues at concentrations up to 0.11 ppm on a DM basis. Less than one percent of samples contained tetracycline residues at concentrations up to 1.12 ppm on a DM basis. None of samples contained tylosin residues. Additionally, 1.3% of samples contained virginiamycin residues at concentrations up to 0.6 ppm on a DM basis. Only one residue sample inhibited growth of E. coli at 104 CFU/g, but this sample contained none of the five antibiotic residues evaluated. No residues inhibited L. monocytogenes growth. These data suggest the likelihood of detectable residues in DG is low, and if they are present, they are found at very low concentrations. It appears that antibiotic residues in DG are inactivated during the production process or are present in sublethal concentrations. There is concern that low concentrations of antibiotics in DG may lead to development of antibiotic resistance in bacteria, especially if antibiotics are present in sublethal doses. However, the risk to human health appears to be minimal. Therefore, future studies on the utilization of antibiotics in ethanol fermentation should focus on the transfer of antibiotic-resistant genes through the ethanol fermentation process and resulting DG production.
  • Thumbnail Image
    Item
    Source, Fall 2010
    (University of Minnesota Extension, 2010) University of Minnesota Extension